Preparation method of sodium zirconate doped material and application of sodium zirconate doped material in thermochemical energy storage

Abstract

The invention provides a preparation method of a sodium zirconate doped material and application of the sodium zirconate doped material in thermochemical energy storage, and relates to the technical field of energy storage material preparation. The sodium zirconate doped material is prepared through solid-phase reaction of Na2ZrO3, Fe2O3 and / or K2CO3, the doping amount of Fe and K in Na2ZrO3 can be regulated and controlled by regulating and controlling the adding amount of all the raw materials, the light absorption and CO2 adsorption performance of the Na2ZrO3-based heat carrier can be enhanced under the specific doping amount, the sodium zirconate doped material is endowed with excellent circulating energy storage capacity, sunlight absorption capacity and high CO2 capture efficiency, and the sodium zirconate doped material has the advantages of being simple in preparation method, low in cost and high in application value. Experiments show that when the doping amount of Fe is 10%, the doping amount of Fe is 10% and the doping amount of K is 3%, the prepared doped material shows excellent cyclic energy storage performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage material preparation, and particularly relates to a preparation method of sodium zirconate doped material and application of the sodium zirconate doped material in thermochemical energy storage. BACKGROUND

[0002] Thermochemical Energy Storage (TCES) realizes energy storage and release through the breaking and recombination of molecular bonds in reversible chemical reactions. This process utilizes the high enthalpy change characteristics of chemical reactions, enabling efficient energy storage and on-demand release when needed. Common TCES materials include carbonate systems, hydroxide systems, metal hydride systems, and metal oxide systems, as well as sulfur, organic matter, and ammonia decomposition systems. These materials have different reaction characteristics and are suitable for different application scenarios. The carbonate system is the most widely used material due to its unique combination of high energy storage density and low cost. Its advantages include high conversion rates for both calcination and carbonation reactions, with few side reactions; both forward and reverse reactions occur at high temperatures, with fast reaction rates; the entire cycle process does not require the use of catalysts, saving system costs; the nature of gas-solid reactions makes it easy to separate the decomposition products without additional operations, simplifying the system process; and calcium is easy to extract, widely distributed, and has high storage capacity and economic efficiency. However, as the number of cycles increases, sintering becomes more severe, leading to a significant decline in energy storage performance and low cycle stability. How to slow down this phenomenon is also a popular research direction.

[0003] Among the numerous candidate materials, sodium zirconate (Na2Zr03) has gradually become a research hotspot due to its unique physicochemical properties, including relatively low regeneration temperature and good cycle stability and strong anti-sintering ability, providing new possibilities for efficient thermochemical energy storage. The advantages of sodium zirconate as a TCES material lie in its excellent performance in multiple aspects. First, its energy storage capacity is relatively high, with a theoretical energy storage density of more than 500 kJ / kg (the specific value varies depending on the reaction conditions and doping modification), far exceeding traditional sensible heat storage materials (such as molten salts, about 200-400 kJ / kg). This is due to the high enthalpy change of the reaction between Na2Zr03 and CO2, allowing unit mass of material to store more thermal energy. Second, compared to other high-temperature TCES materials (such as CaCO3, with a decomposition temperature of >800°C), the regeneration temperature of Na2Zr03 is relatively low (about 700-750°C), reducing the demand for energy input and thus improving the overall thermal efficiency of the system. In addition, sodium zirconate has good chemical stability during the cycle process, and its main component ZrO2 has a very high melting point (about 2700°C) and heat shock resistance, which can maintain the integrity of the structure in a high-temperature environment. This characteristic theoretically enables it to withstand hundreds of energy storage / release cycles while maintaining high reactivity. Existing research has shown that the adsorption capacity of Na2Zr03 in a pure CO2 atmosphere can reach more than 80% of the theoretical value, and it still shows good stability after multiple cycles.

[0004] The thermochemical energy storage process of sodium zirconate (Na2Zr03) is based on its reversible reaction with CO2: In a solar-driven CSP system, the energy storage process of sodium zirconate is divided into two stages. During the storage stage, sunlight is concentrated by a concentrating device into a solar calciner, which calcines Na2Zr03 and ZrO2 at high temperatures (usually >700°C) to decompose into Na2Zr03 and CO2. This endothermic reaction converts solar energy into chemical energy stored in the molecular structure of Na2Zr03, and the released CO2 can be collected or directly used for subsequent cycles. In the energy release stage, Na2Zr03 is introduced into a carbonization reactor to undergo an exothermic reaction with CO2 at a suitable temperature (usually 500-700°C) to generate Na2CO3 and ZrO2, releasing the stored thermal energy. Subsequently, the "hot" CO2 produced by the reaction can enter a turbine to drive power generation, while the regenerated Na2Zr03 and ZrO2 are stored for use in the next cycle. This closed-loop system not only achieves efficient storage and utilization of solar energy, but also is highly compatible with third-generation CSP technologies such as supercritical CO2 (S-CO2) power cycles, and has broad application prospects.

[0005] The specific working principle of sodium zirconate can be further understood from its reaction kinetics and microstructure characteristics. In the carbonation stage (exothermic reaction), CO2 molecules enter the interior of Na2ZrO3 particles through surface adsorption and diffusion, and react with Na + and ZrO3 2- to generate Na2ZrO3 and ZrO2. This process is limited by the diffusion rate of CO2 and the surface area of the particles, so the porosity and particle size of the material are crucial to its performance. In the calcination stage (endothermic reaction), high temperature drives the decomposition of Na2CO3 and ZrO2, releasing CO2 and regenerating Na2ZrO3. This process requires overcoming a high activation energy, but due to the high thermal stability of ZrO2, the reaction system can maintain good structural integrity at high temperatures. The unique advantage of Na2ZrO3 is that its reaction product ZrO2 can act as an inert support framework, reducing particle agglomeration and sintering at high temperatures, thereby improving cycle life. In addition, the raw materials for synthesizing Na2ZrO3, such as Na2CO3 and ZrO2, are relatively low in cost and widely available, making it economically viable, which further enhances its potential for industrial application.

[0006] Despite the above advantages of sodium zirconate, its energy storage performance still faces challenges in practical applications, especially in the degradation problem during multiple energy storage / release cycles. Studies have shown that the performance degradation of Na2ZrO3 heat carriers is mainly due to sintering at high temperatures. During continuous high-temperature calcination, the active sites on the particle surface gradually decrease, and the pore structure collapses, leading to increased CO2 diffusion resistance and decreased reaction rate. For example, Alcántar-Vázquez et al. found that unmodified Na2ZrO3 had a significant decrease in surface area after cycling, with an adsorption capacity of about 3.8 mmol / g, down from the initial 5.5 mmol / g. In addition, Na2ZrO3 has limited light absorption capacity, which cannot be directly and efficiently utilized for solar energy, which limits its application in volumetric solar receivers. These problems have prompted global researchers to focus on improving the performance of Na2ZrO3 through various strategies, including doping modification, microstructure optimization, and process improvement.

[0007] Therefore, it is necessary to design an improved preparation method of sodium zirconate doped material and its application in thermochemical energy storage to solve the above problems. SUMMARY

[0008] The purpose of the present application is to provide a preparation method of sodium zirconate doped material and its application in thermochemical energy storage.

[0009] To achieve the above-mentioned purpose of the application, in one aspect, the present application provides a sodium zirconate doped material, comprising Na2ZrO3 and a metal M doped therein, the metal M being iron and / or potassium; the doping amount of the metal M in the sodium zirconate doped material being 1-20%.

[0010] In another aspect, the present application provides a preparation method of sodium zirconate doped material, comprising the following steps:

[0011] Preparation of Na2ZrO3 with Na2CO3 and ZrO2 as raw materials;

[0012] After the Na2ZrO3 and the precursor of metal M are uniformly mixed, the sodium zirconate doped material is prepared by calcination treatment; the precursor of metal M is the corresponding salt or oxide of iron and / or potassium.

[0013] Preferably, the precursor of metal M is Fe2O3, and the molar amount of Na2ZrO3, Fe2O3 satisfies: Na:Zr:Fe=2:1:x, and the value range of x is 0.01-0.2.

[0014] Preferably, x is any value in 0.01, 0.03, 0.05, 0.10, 0.15, 0.2.

[0015] Preferably, when the precursor of metal M is Fe2O3 and K2CO3, the molar amount of Na2ZrO3, Fe2O3, K2CO3 satisfies: Na:Zr:Fe:K=2:1:0.10:y, and the value range of y is 0.01-0.10.

[0016] Preferably, y is any value in 0.01, 0.03, 0.05, 0.10.

[0017] Preferably, the temperature of the calcination treatment is 900℃, and the time is 5h.

[0018] Preferably, the adding amount of Na2CO3 and ZrO2 in the preparation process of Na2ZrO3 satisfies the molar ratio of Na and Zr is 2:1.

[0019] In particular, the sodium zirconate doped material prepared by the preparation method provided by the present application can be applied to thermochemical energy storage.

[0020] The present application has the following beneficial effects:

[0021] 1、The sodium zirconate doped material provided by the present application is prepared by solid phase reaction of Na2ZrO3, Fe2O3 and / or K2CO3, by adjusting the adding amount of each raw material, the doping amount of Fe, K in Na2ZrO3 can be adjusted, under specific doping amount, the light absorption and CO2 absorption performance of Na2ZrO3 based heat carrier can be enhanced, and the sodium zirconate doped material is endowed with excellent cyclic energy storage capacity, solar light absorption capacity and high CO2 capture efficiency.

[0022] 2、The sodium zirconate doped material provided by the application, by doping Fe into Na2ZrO3, not only can utilize the characteristics of Fe capable of forming dark color phase (such as Fe2O3) to regulate the color of the sodium zirconate doped material, so as to improve the light absorption capacity thereof, in addition, the Fe oxide has a high melting point, which can enhance the sintering resistance and cycle stability of Na2ZrO3 to a certain extent, so as to avoid the performance degradation of the material in multiple energy storage / release cycles, and meanwhile, by doping Fe and K into Na2ZrO3, the synergistic effect between the two can be utilized to improve the CO2 adsorption performance of the sodium zirconate doped material. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 XRD patterns of LA and LFe prepared in Example 1 of the application;

[0024] Figure 2 Optical photos of the sodium zirconate doped materials prepared in Examples 1 to 4 of the application with different Fe doping rates and LA;

[0025] Figure 3 Cyclic energy storage performance test results of LA prepared in Example 1 of the application at different temperatures;

[0026] Figure 4 Cyclic energy storage performance test results of the sodium zirconate doped materials prepared in Examples 1 to 4 of the application with different Fe doping rates at 800℃;

[0027] Figure 5 Carbonization conversion rate results of the sodium zirconate doped materials prepared in Examples 1 to 4 of the application;

[0028] Figure 6 Spectral absorption rate curves and average spectral absorption rate of LA and LFe10 prepared in the application in the wavelength range of 300-1000nm;

[0029] Figure 7 XRD pattern of LFe10K3 prepared in the application;

[0030] Figure 8 Cyclic energy storage test results of the sodium zirconate doped materials prepared in Examples 5 to 8 of the application and LFe10;

[0031] Figure 9 Cyclic energy storage test results of LBFe10 prepared in Comparative Example 1 of the application and LFe10 prepared in the example. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the application more clear, the application is described in detail below with reference to the drawings and specific examples.

[0033] It should be noted that, in order not to obscure the present application with unnecessary details, only the structures and / or processing steps closely related to the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0034] It should also be noted that the terms "comprising", "containing", or any other variant thereof, are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or inherent to such a process, method, article or device.

[0035] In one aspect, the present application provides a sodium zirconate doped material, which comprises Na2ZrO3 and a metal M doped therein, the metal M being iron and / or potassium.

[0036] In another aspect, the present application also provides a preparation method of the above-mentioned sodium zirconate doped material, comprising the following steps:

[0037] Preparation of Na2ZrO3 with Na2CO3 and ZrO2 as raw materials;

[0038] After the Na2ZrO3 and the precursor of the metal M are uniformly mixed, calcination treatment is performed to obtain the sodium zirconate doped material.

[0039] In some embodiments, the amounts of Na2CO3 and ZrO2 added satisfy a molar ratio of Na to Zr of 2:1.

[0040] In some embodiments, the precursor of the metal M is a salt or an oxide corresponding to iron and / or potassium, and preferably Fe2O3 and K2CO3. When the precursor of the metal M is Fe2O3, the molar amounts of Na2ZrO3 and Fe2O3 satisfy: Na:Zr:Fe=2:1:x, x has a value in a range of 0.01-0.2, and specifically any one of 0.01, 0.03, 0.05, 0.10, 0.15, 0.2, corresponding to a doping amount of Fe of 1%, 3%, 5%, 10%, 15%, and 20%, respectively, and x has a value preferably in a range of 0.01-0.1. When the precursor of the metal M is Fe2O3 and K2CO3, the molar amounts of Na2ZrO3, Fe2O3, and K2CO3 satisfy: Na:Zr:Fe:K=2:1:0.10:y, y has a value in a range of 0.01-0.10, and specifically any one of 0.01, 0.03, 0.05, 0.10, corresponding to a doping amount of K of 1%, 3%, 5%, and 10%, respectively.

[0041] In some embodiments, the temperature of the calcination treatment is 900℃, the time is 5h, and the temperature rising rate from room temperature to 900℃ is 5℃ / min.

[0042] The preparation method of the sodium zirconate doped material and the application thereof in thermochemical energy storage are further described below in combination with specific examples.

[0043] Example 1

[0044] In this example, a sodium zirconate doped with iron is prepared, and the preparation method thereof comprises the following steps:

[0045] Na2CO3 (analytical pure) and ZrO2 (analytical pure) are placed in an alumina crucible, ground for 30 min, and mixed uniformly, then the crucible is placed in a muffle furnace, heated to 900 ℃ at a heating rate of 5 ℃ / min, and calcined for 5 h in an air atmosphere. After calcination is completed, the sample is taken out after cooling to room temperature, and is continuously ground into fine powder, which is named as LA. The addition amount of Na2CO3 and ZrO2 satisfies the molar ratio of Na and Zr of 2:1, and the heating rate from room temperature to 900 ℃ is 5 ℃ / min. In particular, in order to compensate for the possible sodium volatilization in the high-temperature calcination process, 1% of Na2CO3 by mole is additionally added.

[0046] LA and Fe2O3 (analytical pure) are placed in an alumina crucible, ground for 30 min, and mixed uniformly, then the crucible is placed in a muffle furnace, heated to 900 ℃ at a heating rate of 5 ℃ / min, and calcined for 5 h in an air atmosphere. After calcination is completed, the sample is taken out after cooling to room temperature, and is continuously ground into fine powder, which is the sodium zirconate doped with iron, and is named as LFe1. The mass of LA and Fe2O3 satisfies the molar ratio of Na:Zr:Fe of 2:1:0.01, the doping amount of iron in the sodium zirconate doped with iron is 1%, and the heating rate from room temperature to 900 ℃ is 5 ℃ / min. It should be noted that, unless otherwise specified, the reagents and raw materials used in the examples of the present application can be obtained by market purchase.

[0047] The XRD patterns of LA and LFe1 are shown in the A graph and the B graph of FIG. 1, respectively. Figure 1 It can be seen from the graph that the main diffraction peaks of LFe1 belong to Na2ZrO3, which indicates that the crystal phase structure of Na2ZrO3 remains stable after Fe is doped therein. Meanwhile, the diffraction peaks of Fe2O3 are also observed in LFe1, which indicates that Fe is partially incorporated into the material in the form of a secondary phase, which may be caused by the lattice distortion caused by the partial substitution of Zr by Fe 3+ with a smaller ionic radius 4+ ; in addition, the diffraction peaks of Na2CO3 and ZrO2 can also be observed in LFe1, and the XRD results show that the doping of Fe not only introduces a new phase, but also causes a certain degree of change in the crystal structure of Na2ZrO3.

[0048] Examples 2 to 4

[0049] The difference between Examples 2 to 4 and Example 1 is only that the addition amount of LA and Fe2O3 is different, specifically, the molar ratio of Na:Zr:Fe in LA and Fe2O3 is different from Example 1, the molar ratio of Na:Zr:Fe in Example 2 is 2:1:0.05, the molar ratio in Example 3 is 2:1:0.1, and the molar ratio in Example 4 is 2:1:0.2, and the obtained products are named as LFe5, LFe10, LFe20 in turn, and the rest of the experimental conditions are the same as Example 1, which will not be repeated here.

[0050] The optical photographs of the iron-doped sodium zirconate materials prepared in Examples 1 to 4 and LA under different Fe doping rates are shown in FIG. 1. Figure 2 The results show that the color of the material after doping Fe is significantly darker than that of LA, and the color of the material gradually deepens with the increase of the Fe doping amount. Specifically, the color of Na2ZrO3 is light brown, while the color of Na2ZrO3 doped with 0.05Fe is light brown, the color of Na2ZrO3 doped with 0.1Fe is light brown, and the color of Na2ZrO3 doped with 0.2Fe is dark brown. 1.9 Fe 0.01 ZrO3 1.8 Fe 0.2 ZrO3 The color change indicates that the doping of Fe changes the surface optical properties of the material, which may be related to the reorganization of the electronic structure and the formation of iron oxide phase.

[0051] The cyclic energy storage performance of the synthesized materials was evaluated using a double fixed bed reactor (model: OFT-1200X-II). During the performance test of LA, the sample was placed in the reaction boat, first calcined at 750°C, 800°C, 850°C for 20 min in the energy storage zone under pure N2 atmosphere, then transferred to the energy release zone and exposed to 900°C for 30 min under pure CO2 atmosphere, and the total gas flow was controlled at 1 L / min. Each group was subjected to 10 cycles, and after each cycle, the sample was taken out and cooled to room temperature in air. The mass of the sample after calcination and carbonization was recorded respectively. During the performance test of iron-doped materials and iron-potassium co-doped materials, the sample was placed in the reaction boat, first calcined at 800°C for 20 min in the energy storage zone under pure N2 atmosphere, then transferred to the energy release zone and exposed to 900°C for 30 min under pure CO2 atmosphere, and the total gas flow was controlled at 1 L / min. Each group was subjected to 10 cycles, and after each cycle, the sample was taken out and cooled to room temperature in air. The mass of the sample after calcination and carbonization was recorded respectively.

[0052] To quantitatively evaluate the energy storage performance of the heat carrier, the energy storage density (Q n , unit: kJ / kg) and carbonization conversion rate (X n , unit: %) of Na2ZrO3 heat carrier were defined and calculated by formula (2) and formula (3) respectively:

[0053] wherein N represents the number of cycles, used to mark the cycle experiment; m car,N is the mass of the sample after the Nth carbonization (unit: g), that is, the total mass after Na2ZrO3 reacts with CO2 to generate Na2CO3 and ZrO2; m cal,N is the mass of the sample after the Nth calcination (unit: g), representing the mass recovered as pure Na2ZrO3; ΔH 0 r is the standard reaction enthalpy of the carbonization reaction of Na2ZrO3 with CO2 (unit: kJ / mol); M CO2 is the molar mass of CO2 (44 g / mol); the coefficient 1000 is used to convert the energy unit from J to kJ; M Na2ZrO3 is the molar mass of Na2ZrO3 (about 185 g / mol), used to calculate the theoretical molar number of the sample; φ is the content of Na2ZrO3 in the doped sample.

[0054] The results of the cyclic energy storage performance test of LA at different temperatures are shown in Figure 3 The results show that the carbon dioxide adsorption performance of LA at different temperatures all presents a downward trend and continues to decline with the increase of the number of cycles. Specifically, from the first cycle to the tenth cycle, the performance of LA at an adsorption temperature of 800℃ is better than that at 750℃ and 850℃, and all samples present a significant downward trend after the first cycle, and the degree of decline tends to be stable. The carbon dioxide adsorption capacity of LA at 800℃ reaches 0.201 g / g in the first cycle, and decreases to 0.153 g / g in the tenth cycle; the carbon dioxide adsorption capacity of LA at 750℃ reaches 0.181 g / g in the first cycle, and decreases to 0.146 g / g in the tenth cycle; the carbon dioxide adsorption capacity of LA at 850℃ reaches 0.189 g / g in the first cycle, and decreases to 0.129 g / g in the tenth cycle. Overall, the carbon dioxide adsorption capacity of LA at an adsorption temperature of 800℃ is optimal, although the carbon dioxide adsorption capacity in the first cycle at 750℃ is less than that at 850℃, but the performance in the subsequent cycles is better than that at 850℃.

[0055] Further, the cyclic energy storage performance of the iron-doped sodium zirconate material at 800℃ was also studied during the experiment, and the test results are shown in Figure 4As shown, the results show that the carbon dioxide adsorption performance of all samples presents a downward trend and continues to decline with the increase of cycle number, except that the adsorption performance of the sample with a doping ratio of 0.2 is significantly lower than that of all other test samples, and the samples with a doping ratio of 0.01, 0.05 and 0.1 all show similar curves to the LA control group. Specifically, at an adsorption temperature of 800℃, the carbon dioxide adsorption capacity of LFe in the first cycle reached 0.205g / g, and in the tenth cycle it dropped to 0.151g / g; the carbon dioxide adsorption capacity of LFe5 in the first cycle reached 0.210g / g, and in the tenth cycle it dropped to 0.155g / g; the carbon dioxide adsorption capacity of LFe10 in the first cycle reached 0.203g / g, and in the tenth cycle it dropped to 0.149g / g; the carbon dioxide adsorption capacity of LFe20 in the first cycle reached 0.187g / g, and in the tenth cycle it dropped to 0.139g / g; except for LFe20, the carbon dioxide adsorption capacity of all samples in the first cycle was higher than that of LA, which may be due to the formation of crystal lattice vacancies promoting CO2 diffusion Fe 3+ (ion radius about ) partially replace Zr 4+ (ion radius about ) or Na + (ion radius about ) After the replacement, due to charge imbalance and ion size difference, oxygen vacancies or cation vacancies may be introduced into the Na2ZrO3 lattice, which provides additional diffusion channels for CO2 molecules, thereby reducing the diffusion resistance and making CO2 more easily enter the material interior to react with active sites. For the LFe20 sample, due to the large amount of doping leading to a decrease in the effective component, the overall adsorption capacity performs poorly. Although the performance of the iron-doped samples in the first cycle is better than that of LA, the efficiency of performance improvement is very limited, and the carbon dioxide adsorption capacity of the iron-doped samples is generally lower than that of LA after 5 cycles.

[0056] The iron-doped sodium zirconate materials prepared in Examples 1 to 4 were carbonized in a pure CO2 atmosphere for 30min, and the carbonization conversion rate results are shown in Figure 5 The results show that the carbonization conversion rate of the LFe20 sample is the best, decreasing from 97.99% to 73.03% within ten cycles, followed by LFe10 from 94.75% to 69.59% and LFe5 from 90.93% to 67.64%. The three are quite different, but since the carbon dioxide adsorption capacity of the LFe20 sample is significantly lower than the other two in Figure 4 , it indicates that the carbon dioxide adsorption effect of LFe10 is the best.

[0057] The spectral absorption rate curves of LA and LFe10 in the wavelength range of 300-1000nm are shown in Figure 6As shown in FIG. A of FIG. 1, the results show that the absorption rate of LA is low, with a maximum of only 10%, reflecting its high reflection characteristics. After Fe doping, the absorption rate is significantly improved, especially in the range of 300-600 nm. The absorption rate of LFe10 at 300 nm is the highest value of 97%, and then starts to decrease to about 65%. As the wavelength increases to 400-600 nm, the absorption rate of all Fe-doped samples gradually tends to be flat, but is still significantly higher than that of the pure sample, but starts to decrease significantly to 12% in the range of 600-1000 nm. To quantitatively compare the solar energy absorption capacity, Figure 6 FIG. B of FIG. 1 gives the average spectral absorption rate (A sol ) of each sample. The following formula is used to calculate the average light absorption rate: where λ represents the wavelength, in nm; A(λ) represents the measured solar absorption rate, in percentage; IAM1.5D represents the spectral irradiance measured under the standard solar spectrum (AM1.5D direct); λ1 and λ2 are the starting and ending wavelengths, respectively, in nm. Between 300 nm and 800 nm, the A sol of LA is about 1% or so, while the A sol of the LFe10 sample is about 53.34%. Between 300 nm and 1000 nm, the A sol of LA is about 0.7% or so, while the A sol of the LFe10 sample is about 44%. The solar energy capture efficiency of LFe10 is significantly higher than that of LA, indicating that the doping of Fe significantly improves the solar energy capture efficiency of Na2ZrO3.

[0058] Examples 5 to 8

[0059] A sodium zirconate material doped with iron and potassium was prepared according to Examples 5 to 8, and the preparation method was as follows: the mixture was ground for 30 min in an alumina crucible, then the crucible was placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min, and calcined in an air atmosphere for 5 h. After calcination, the sample was cooled to room temperature and taken out, and then ground into fine powder, named LA. The addition amount of Na2CO3 and ZrO2 satisfies the molar ratio of Na to Zr of 2:1. In particular, to compensate for the possible volatilization of sodium during high-temperature calcination, 1% of Na2CO3 was additionally added.

[0060] LA, Fe2O3 (analytical grade), and K2CO3 (analytical grade) were ground in an alumina crucible for 30 minutes to mix thoroughly. The crucible was then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min. The crucible was then calcined in air for 5 hours. After cooling to room temperature, the sample was removed and ground into a fine powder to produce the iron-doped sodium zirconate material. The molar ratio of Na2CO3, ZrO2, Fe2O3, and K2CO3 satisfies Na:Zr:Fe:K = 2:1:0.10:y, where y is 0.01, 0.03, 0.05, and 0.10, corresponding to K doping levels of 1%, 3%, 5%, and 10%, respectively. The resulting products are named LFe10K1, LFe10K3, LFe10K5, and LFe10K10, respectively. To compensate for potential sodium volatilization during the high-temperature calcination, an additional 1 mol% of Na2CO3 was added.

[0061] The XRD pattern of LFe10K3 is as follows Figure 7 As shown, its overall diffraction peak is similar to that of LFe1 in Example 1, and the overall diffraction peak is similar to that of the iron-doped sample, but no diffraction peak of K or other K compounds can be found. The possible reason is that the amount of potassium doping is too small to be detected. Potassium, as an alkali metal element, has high volatility. At high temperatures, K may partially volatilize in gaseous form (such as K2O) or migrate to the sample surface to form an amorphous layer, resulting in a decrease in the K content inside the crystal and an inability to form a detectable crystalline phase.

[0062] The cycle energy storage test results of the iron and potassium doped sodium zirconate materials and LFe10 prepared in Examples 5 to 8 are as follows: Figure 8 As shown, the results show that after K doping, the cyclic energy storage performance of the material is improved. Specifically, the carbon dioxide adsorption capacity of LFe10K1 in the first cycle reached 0.216g / g, and decreased to 0.163g / g in the tenth cycle; the carbon dioxide adsorption capacity of LFe10K3 in the first cycle reached 0.206g / g, and decreased to 0.172g / g in the tenth cycle; the carbon dioxide adsorption capacity of LFe10K5 in the first cycle reached 0.211g / g, and decreased to 0.164g / g in the tenth cycle; the carbon dioxide adsorption capacity of LFe10K10 in the first cycle reached 0.211g / g, and decreased to 0.146g / g in the tenth cycle. Among them, except for the LFe10K10 sample, the carbon dioxide adsorption capacity of the other iron-potassium co-doped samples was higher than that of the iron-doped samples. The LFe10K1 sample reached the highest value of 0.216g / g in all experiments in the first cycle, while the theoretical maximum adsorption capacity of sodium zirconate material is 0.238g / g. However, a comparison of ten cycles revealed that the LFe10K3 sample had a significant decline in the second cycle, and maintained a relatively stable carbon dioxide adsorption capacity in subsequent cycles, with a significant advantage after the fifth cycle.

[0063] Comparative Example 1

[0064] Comparative Example 1 and Example 1 differ only in the preparation method of Na2ZrO3, specifically, after grinding for 30 min in an alumina crucible, the crucible was placed in a muffle furnace, heated to 900℃ at a rate of 5℃ / min, and calcined for 5h under air atmosphere. After calcination, the sample was removed after cooling to room temperature, and further ground into fine powder to obtain the iron-doped sodium zirconate material, which was named LBFe10.

[0065] The results of the cyclic energy storage test of LBFe10 and LFe10 are shown in Figure 9 The results show that the performance of LFe10 prepared from Na2ZrO3 precursor is significantly better than that of LBFe10, indicating that the sodium zirconate doped material prepared from Na2ZrO3 precursor has better performance. This is because: when mixed with Fe2O3 to prepare the doped material, Na2ZrO3 can provide uniformly distributed Na and Zr active sites, which is beneficial to the formation of stable doped structure; during the reaction process, the interface reaction of Na2ZrO3 and Fe2O3 is more controllable, which may form a uniform solid solution or composite phase, thereby improving the structural stability and CO2 adsorption / desorption performance of the material. For LBFe10, during the high-temperature synthesis process, Na2CO3 needs to be decomposed (release CO2) and react with ZrO2 to form Na2ZrO3, which may cause local stoichiometric ratio imbalance or incomplete reaction; in addition, the chemical inertness of ZrO2 may delay the formation of Na2ZrO3, resulting in non-uniform microstructure of the synthesized product, such as the existence of local Na-rich or Zr-rich regions. This non-uniformity may reduce the active site density of the material, and thus affect the CO2 cyclic energy storage performance.

[0066] The above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A sodium zirconate doping material, characterized in that The sodium zirconate doping material comprises Na2ZrO3 and a metal M doped therein, wherein the metal M is iron and / or potassium; the doping amount of the metal M in the sodium zirconate doping material is 1-20%.

2. A method for preparing the sodium zirconate doping material according to claim 1, characterized in that: The steps include: Na2ZrO3 was prepared using Na2CO3 and ZrO2 as raw materials; Na2ZrO3 and a precursor of metal M are mixed evenly and then calcined to obtain a sodium zirconate doping material; the precursor of metal M is a salt or oxide corresponding to iron and / or potassium.

3. The preparation method according to claim 2, characterized in that The precursor of the metal M is Fe2O3, and the molar amounts of Na2ZrO3 and Fe2O3 satisfy: Na:Zr:Fe=2:1:x, where the value of x is in the range of 0.01-0.

2.

4. The preparation method according to claim 3, characterized in that x is any value of 0.01, 0.03, 0.05, 0.10, 0.15, or 0.

2.

5. The preparation method according to claim 2, characterized in that When the precursors of the metal M are Fe2O3 and K2CO3, the molar amounts of Na2ZrO3, Fe2O3 and K2CO3 satisfy: Na:Zr:Fe:K=2:1:0.10:y, and the value range of y is 0.01-0.

10.

6. The preparation method according to claim 5, characterized in that y is any value among 0.01, 0.03, 0.05, and 0.

10.

7. The preparation method according to claim 2, characterized in that The calcination temperature is 900° C. and the calcination time is 5 hours.

8. The preparation method according to claim 2, characterized in that During the preparation of Na2ZrO3, the added amounts of Na2CO3 and ZrO2 satisfy the molar ratio of Na to Zr of 2:

1.

9. Use of a sodium zirconate doped material prepared by the preparation method according to any one of claims 2 to 8 in thermochemical energy storage.

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